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Charging system problems

Discussion in 'The Garage' started by jhark37, Oct 7, 2018.

  1. jhark37

    jhark37 XS400 Member

    Hi, All,

    Relatively new to the forum and the xs. Just completing a restoration of an 82 xs400 Seca. Starts and runs OK, although it will need a little carb tuning.

    Problem is the charging system is not working. Have measured 4.9 ohms on the rotor and about 1.0 on
    the 3 white field coil leads. Rotor is to spec, but field coil should be .5, if I rremember correctly. Anyway, get no voltage output from the generator. Test leads on battery with the engine running show just basic battery
    voltage, not the 14 - 14.5 I'd expect. What do you all suggest as a next step?

    Thanks, John
  2. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    You should be getting 14-15v at a cruising RPM, above 3k. Ive installed a volt meter gauge on my bike so I know whats happening. Losing battery/charging power in the middle of the night is no fun, ask me how I know...

    When I turn the headlight on, I loose 1 volt. It also depends on how charged the battery is and how long its been sitting. If I ride everyday, cruising voltage will be around 14-14.5v, remove one V if I use the lights. If the bike sits for a couple days, the volts will stay at 15v when cruising to charge.
  3. jhark37

    jhark37 XS400 Member

    Thanks for taking the time to reply. But what I'm really looking for is what are the likely culprits? I can think of 4, maybe there are more. Regulator, brushes, rotor or stator. Suggestions as to most likely cause?

    Thanks, John
  4. jhark37

    jhark37 XS400 Member

    Like to revisit this issue. Have used "Curleys Troubleshooting Guide". Have also replaced the regulator with a brand new one. If I ground the green wire on the regulator connector, the charging system works. Get 14+ at the battery. Curley gives 2 possibilities, bad regulator or bad regulator ground. As I said,
    regulator is brand new and black wire from regulator tests good for ground.

    Where to now? Any ideas? Is it safe to leave the green wire grounded for a long term solution?

    Thanks, John
  5. BBS360

    BBS360 XS400 Guru Top Contributor

    You'd be running the alternator at maximum output all the time. Could burn out the stator or field coil.
    Would also be boiling your battery.

    Which specific regulator did you buy?
  6. jhark37

    jhark37 XS400 Member

    Bought regulator on Amazon, believe it or not. Listed specific part # for an
    82 Seca 400. I suppose something could be wrong with it, but it would be hard
    to believe! Wire colors are correct, fits the connector, etc.
  7. jhark37

    jhark37 XS400 Member

    I know there has not been much interest in this thread, but thought I'd close the loop anyway. As I mentioned earlier, I had purchased
    a new regulator with no change in the results. Hard to believe I had 2 nonfunctioning regulators. But true. Finally got a good one
    and the system works. 14+ volts at the battery. I've also tried to reduce the load by using LED tail/brake lights as well as an LED
    headlight. Like the look, too. Have finally finished the restoration and am VERY pleased with the result. What a great bike!

    Cheers, John
  8. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    I once bought a new "plug and play" rec/reg combo that plugged into the stock harness. I didnt work either. What a waste of $100.

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